Universal cellular cofferdam with embedded columnar framing and embedded rock anchor mechanism

ABSTRACT

One embodiment of Universal Cellular Cofferdam with embedded prefabricated columnar framing ( 10 ), embedded rock anchors ( 16 ), pile cap ( 25 ), cofferdam perimeter skin ( 15 ) and granular fill ( 22 ) constitutes a hybrid cofferdam structure comprising columnar framing and cofferdam gravity cell. The described structure utilizes resisting mechanisms of structural framing, cofferdam gravity forces and mechanism of rock anchor devices for creation of unique resisting mechanism where all three resisting mechanisms compliment each other, preventing modes of structural failures typical for gravitational or columnar structures alone.

A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.

CROSS REFERENCES TO RELATED APPLICATIONS

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FEDERALLY SPONSORED RESEARCH

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SEQUENCE LISTING OR PROGRAM

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BACKGROUND

1. Field

This application relates to cofferdams, specifically to non-traditional cellular cofferdam with embedded prefabricated framing and embedded rock anchor.

2. Prior Art

Traditionally cellular cofferdams are utilized for such waterfront devices as mooring and breasting dolphins, quay walls at deep water port berthing facilities, and for bridge protection devices designed for protection of the bridge piers from the extremely high lateral load of the ship collision impact.

Original cellular cofferdam was designed as an open ended cellular can structure filled with granular material.

The first close cell cofferdam was designed by General Harley B. Ferguson and Charles S. Boardman in 1911. The first fully successful modern day full circle cofferdam was constructed on Ohio River in 1928 by J. S. Miller and Dravo Corporation.

Construction of the cell cofferdam requires in situ installation of highly complicated template framing with consequent construction of the cofferdam skin consisting of flat sheet piling forming a circular can. Traditional close cell cofferdam works as a gravitational structure, deriving sliding and overturning stability from the gravity and sliding resistance of the cofferdam cell granular fill, hoop forces developing in the skin of the cofferdam and shear forces developing in the granular material of the cofferdam fill.

Typical failure modes of the regular cellular cofferdam structure are shown in FIG. 1. Collapse of the close cell cofferdam is caused by the cofferdam can rotation and consequent escape of the granular fill material 22 from the bottom of the cellular can built of the interlocked flat sheet pile sections 15. Cell stability failure is marked by three distinguished slip circle lines A, B, C and sliding plan D. Therefore, stability of the original cofferdam cell depends on capacity restricted by 4 unrestrained failure modes described above.

Thus if at least one of the potential slip surfaces fails, this structure becomes unstable: it slides along the plan D or rotates along one of the slip circles: A, B or C losing stability and structural integrity as granular fill 22 escapes the tilted bottom of the open cell cofferdam structure. Another mode of failure that usually accompanies cofferdam tilting or rotation along the slip circles A, B or C is buckling failure of the cofferdam skin shown in FIG. 1 and depicted by reference numeral 15A.

Several types of the cellular cofferdam modifications have been proposed in the past—for example, in 1921 C. S. Boardman modified his original design, creating means of cofferdam construction in the dry using interior bracing for transporting fully built structure into position.

U.S. Pat. No. 1,398,221

Inventor: Charles S. Boardman

Issued: Nov. 29, 1921

Invention was designed to permit the assembly of the cofferdam with co-acting interior bracing in any convenient location from which it could be lifted as a unit and set into position where sheet piles are released from separable reinforcing cage or bracing form and driven to final tip elevation. The separable reinforcing cage is formed of series of annular circular wales spaced vertically and connected by vertical spacing members. Such arrangement allows central unobstructed opening that permits removing the material from the bottom of excavation. Although, relatively inexpensive to fabricate, this structural system does not address any failure mode challenges presented by the original cellular cofferdam system. The system suffers from a number of disadvantages:

-   -   (a) The weight of the lifted system becomes prohibitively high,         restricting diameter and height of the cofferdam.     -   (b) The system does not resolve stability issues attributed to         the conventional cellular cofferdam systems presently in use.

The U.S. Pat. No. 1,398,221 presents a new method for construction of the conventional cofferdam system.

Another attempt to modify construction method for conventional cofferdam system was presented by Werener W. Burkemper, U.S. Pat. No. 4,419,030.

U.S. Pat. No. 4,419,030

Inventor: Werner W. Burkemper

Issued: Sep. 14, 1981

Burkemper introduced a new method for conventional cofferdam construction. His system comprises a temporary template framing for cofferdam template construction. System designed by Burkemper describes in situ built template for temporary support of shoring cell during the cofferdam cell construction. Burkemper describes temporary structure consisting of plurality of circular rings serving as wales for construction of the open can sheet pile skin and supported by the number of spud piles installed on cell perimeter. Further, Burkemper explains in column 1, lines 54-58 (U.S. Pat. No. 4,419,030) that “After the shoring walls of the cofferdam cell are complete, the template is removed from the interior of the cell and, in some instances, the interior of the cell is filled with sand or other fill material so as to form a cofferdam.”

Burkemper describes the new method of the conventional cofferdam construction with no embedded framing and no permanently embedded rock anchors.

SUMMARY

In accordance with one embodiment, a Universal Cellular Cofferdam with Embedded Columnar Framing and Rock Anchor Mechanism, further called Universal Cellular Cofferdam for simplicity, comprises columnar framing 10 with columns 11 placed on the circumference of the cofferdam circular cell; rock or soil anchors 16 embedded and grouted into the columns of the cofferdam framing and into the reinforced concrete pile cap 25; rock anchors 16 anchored into the bed rock or another competent soil base strata; cofferdam perimeter skin 15 formed of interlocked flat sheet pile sections, and granular fill 22 of the cofferdam cell.

DRAWINGS—FIGURES

In the drawings, closely related figures have the same number.

FIG. 1 shows failure modes of the conventional cellular cofferdam.

FIG. 2 shows failure modes of the Universal Cofferdam

FIG. 3 shows 3-D view of universal prefabricated cofferdam framing. (Sheet pile interlock connector 14 and horizontal truss moment connection plates 18 are not shown for clarity)

FIG. 4 shows Universal Cofferdam framing in plan.

FIG. 5 shows sectional view 5-5 indicated by section line 5-5 in FIG. 4

FIG. 6 shows truss diaphragm connection to the column of the cofferdam framing.

FIGS. 7 and 8 show cofferdam column bearing support.

FIGS. 9 and 10 show Cofferdam lifting hat detail

FIG. 11 show Universal Cofferdam with rock anchors in plan

FIG. 12 shows sectional view 12-12 indicated by section line 12-12 in FIG. 11

FIG. 13 shows Section 13-13 indicated by section line 13-13 in FIG. 11.

FIG. 14, 15 show resistance mechanism of the group of preloaded rock or soil anchors.

DRAWINGS—REFERENCE NUMERALS

10 cofferdam framing assembly

11 Universal Cofferdam column

12 star truss diaphragm

13 Universal Cofferdam wale

14 sheet pile interlock connector

15 flat sheet piling of the cofferdam skin

15A deformed or buckled section of the cofferdam skin

16 rock anchor insert

17 headed studs

18 star truss diaphragm flange to column gusset plate connector

19 column bearing detail

20 lifting hat detail

21 air lock hole

22 granular fill

23 rock socket

24 rock rupture cone

25 concrete pile cap

26 rock anchor grouting outlet/spacer

Abbreviations shown on the figures:

MHV—Mean High Water

MLV—Mean Low Water

BDR—Bed Rock elevation

R.S.—bottom of rock socket hole.

T.B.—base of cofferdam

A—convex surface failure through the granular fill

B—concave shallow surface failure through the base

C—concave deep surface sliding failure

D—plain failure sliding surface

H—lateral destabilizing force

Detailed Description—FIGS. 3, 11, 12, 13, 14 and 15—First Embodiment

One embodiment of the Universal Cellular Cofferdam is illustrated in FIG. 11 (top view of the Universal Cellular Cofferdam framing) and FIGS. 12 and 13 (sections 12 and 13 taken from FIG. 10). The Universal Cellular Cofferdam framing assembly 10 comprises 6 tubular columns 11 interconnected by two levels of star truss diaphragms 12 and two levels of perimeter wales 13. Each end of the star truss diaphragm is connected to the column with gusset plates 18. Skin of the Universal Cellular Cofferdam consists of six segments of interconnected flat sheet pile sections 15 connected to cofferdam columns 11 separating each Universal Cellular Cofferdam skin segment. Extreme sheet pile elements of each sheet pile segment are connected to each column with sheet pile interlock connector 14 welded to column 11.

In the preferred embodiment, the cofferdam framing assembly 10 shown in FIG. 3 is anchored to the soil sub base with rock or soil anchor inserts 16 grouted inside of each column 11 and within predrilled rock socket 23. At the upper end rock anchor inserts 16 are anchored into the reinforced concrete pile cap 25.

In the preferred embodiment, rock or soil anchors inserts have headed studs 17 welded to the body of the anchor insert 16 embedded and grouted inside the rock socket 23; and to the body of the insert 16 embedded into concrete pile cap 25.

Headed studs 17 increase the grip between the concrete of the rock socket 23 and rock anchor insert 16; and between the concrete of the pile cap 25 and rock anchor insert 16 correspondingly. At the bottom end each column 11 of the cofferdam framing 10 is terminated with column bearing detail 19. Bearing detail 19 reduces the bearing pressure under the cofferdam column during the cofferdam framing positioning. Lifting points of each cofferdam column are terminated with removable lifting hat detail 20 with two air lock holes 21 shown in FIGS. 9 and 10. Air lock holes 21 prevent formation of the air plug in the column, and prevent cofferdam framing floatation during cofferdam submergence. In other embodiments Universal Cellular Cofferdam framing 10 can be installed without rock or soil anchors. In that case it will function as a prefabricated columnar template framing for a conventional cofferdam. FIG. 3 shows Universal Cellular Cofferdam framing 10 without cofferdam skin 15 and rock anchor inserts 16.

Advantages

Present art overcomes handicaps of the original TVA design widely used since cofferdam invention. It is based on a different concept of full cellular cofferdam construction utilizing embedded pipe columnar framing as a false work for sheet piling installation; and for anchoring cofferdam to the bedrock. Present art utilizes pipe rock anchors 16 installed through the pipe columns 11 of the Universal Cellular Cofferdam framing 10 as the most rational rock anchor detail. Connection of the rock anchors 16 to the Universal Cellular Cofferdam pile cap 25 enhances Universal Cellular Cofferdam stability arresting Cofferdam skin 15 differential sliding and skin buckling depicted by numeral 15A in FIG. 1.

While regular cellular cofferdams are well suited for the purposes for which they were originally designed, they have more limited load capacity than Universal Cellular Cofferdam of the present art. The lateral load resisted by Universal Cellular Cofferdam by far exceeds the load magnitude resisted by the conventional cellular cofferdam of similar height and diameter.

Features and advantages of the present invention will become more fully appreciated and understood when reviewed in conjunction with accompanying FIGS. 14 and 15.

FIG. 14 shows Universal Cellular Cofferdam framing in plan with a footprint of the engaged truncated rock anchor cones 24 resisting Universal Cellular Cofferdam overturning.

The configuration of the Universal Cellular Cofferdam star truss diaphragm 12 makes force directionality irrelevant.

At least 2 rock anchors 16 are engaged in the Universal Cellular Cofferdam resistance to overturning at any time. FIG. 15 shows the mechanism of the rock anchor in sectional view. Each pair of the truncated rock rupture cones 24 is effectively preloaded by cofferdam granular fill 22. Such arrangement increases pull out capacity of the rock or soil anchors and prevents Universal Cellular Cofferdam rotation. Two rock anchors 16 shown along the horizontal fulcrum axis X′-X′ serve as compression elements of the resisting couple composed of the two tension rock anchor elements and two compression rock anchor elements. Directionality of the fulcrum axis X′-X′ and position of the two engaged tension anchors depends on the directionality of the overturning force H shown in FIGS. 1 and 2. Another advantage of the Universal Cellular Cofferdam system is evident from the enhanced sliding capacity of the cofferdam along the plan D shown in FIG. 2. Sliding resistance of the Universal Cellular Cofferdam becomes the combination of the sliding resistance between the granular fill 22 and cofferdam sub base; and shear resistance capacity of the rock anchor sockets 23 with embedded rock anchors 16. Universal Cellular Cofferdam rock anchor system prevents convex slip circle failure through the granular fill (Line A), and concave slip circle failure through the sub base of the cofferdam (Line B). Similarly, Universal Cellular Cofferdam system prevents deep slip circle failure (Line C). The deep slip circle failure of the Universal Cofferdam can happen only in case of buckling or yielding of the two rock anchors 16 located along the floating fulcrum axis X′-X′. Such mechanism makes Universal Cofferdam more than 10 times stiffer than conventional cofferdam of the similar geometry.

The present art allows great flexibility for usage of Universal Cellular Cofferdam. It can be used for construction of deep water quay walls and dolphins subjected to unusually high lateral loads. However, it becomes the most efficient solution for bridge protection devices, protecting bridge piers from high load of ship and ice collision impact.

While, concept of U.S. Pat. No. 1,398,221 was a step forward from the original art, allowing cofferdam assembly in the dry, it failed to realize benefits of columnar framing and rock anchoring devices for stability of the cellular cofferdam structure. The system described by U.S. Pat. No. 1,398,221 has not eliminated cofferdam skin buckling mode caused by escaping granular fill.

Similarly, concept of U.S. Pat. No. 4,419,030 was just another modification of the currently practiced cellular cofferdam construction method. However, solution suggested by U.S. Pat. No. 4,419,030 was not addressing stability issues of the final cofferdam structure, nor it was claiming a new cofferdam system.

Conclusions, Ramifications, and Scope.

Accordingly, the reader will see that the Universal Cellular Cofferdam of the various embodiments can be used for construction of the conventional cellular cofferdam systems and for anchored cofferdam systems with greatly enhanced resisting capacity to sliding and overturning.

Furthermore, the system has additional advantages in that:

-   -   it allows fabrication of the cofferdam template in the         convenience of the fabrication shop, thus shortening and         eliminating many efforts associated with a field work.     -   it can be easily leveled on site using leveling pads under each         framing column.     -   it permits installation of the rock anchors, significantly         increasing cofferdam resistance to sliding and overturning.     -   columnar framing of the Universal Cellular Cofferdam prevents         cofferdam skin buckling failure typical for conventional         cofferdams with escaping granular fill.

Although the description above contains specificities, these should not be construed as limiting the scope of the embodiments but as merely providing illustrations of some of the presently preferred embodiments.

Thus the scope of the embodiments should be determined by the appended claims and their legal equivalents, rather than by the examples given. 

The present invention claims the following:
 1. Hybrid gravity-columnar system comprising circular prefabricated columnar space framing; perimeter sheet pile infill between the columns of the framing and granular infill confined by a formed barrel herein; rock anchors installed and grouted into bedrock and each column annular space, and anchored into the concrete pile cap of the composite framing, forming composite anchored columnar—gravitational system called Universal Cellular Cofferdam herein.
 2. Prefabricated rigid space framing comprising six pipe columns and two horizontal six end star truss diaphragms consisting of two equally sided triangles having all truss elements of the diaphragm intersected and connected in one plan, serving as an integral structural support and lateral bracing for hybrid gravity-columnar system. 